Definitions of coma:

• noun:   a state of deep and often prolonged unconsciousness; usually the result of disease or injury
• noun:   (astronomy) the luminous cloud of particles surrounding the frozen nucleus of a comet; forms as the comet approaches the sun and is warmed
• noun:   a usually terminal tuft of hairs especially on a seed
• name:  A surname (very rare: popularity rank in the U.S.: #41082)